Different networks provide varying levels of security and users may trust different networks more than other networks. Furthermore, in a large distributed computing system (e.g., multiple distributed data centers) of a computing resource service provider, various customers, users, services, and resources of the computing resource service provider are in frequent communication with each other over various networks and intermediaries. Keeping the system secure becomes more challenging as services and computing resources are added to these large distributed computing systems and as the complexity and usage of these systems increases. In such distributed computing systems, it can be difficult to identify the vulnerabilities of the system. Certain computing devices and/or computing resources may be located in different networks. Furthermore, it can also be difficult to isolate and troubleshoot issues with the system, and even when issues are identified, reliably securing the system may be challenging. In addition, various standards and regulations may require data to be secure when in transit over networks such as the Internet.